In a short range wireless communication or a mobile communication, a microwave band is usually used, particularly the frequency band ranging from 1 GHz to 10 GHz. The communication devices used in these communications are strongly demanded to be downsized and thinned. Also, the electronic component used in the communication devices are also strongly demanded to be downsized and thinned.
Generally, when a signal of a high frequency within a frequency band ranging from 1 GHz to 10 GHz is transmitted, a transmission line configured by combining a conductor and a dielectric is used such as a coaxial line, a strip line, a microstrip a coplanar line or other lines
The electronic component used in the communication devices contains a component containing a resonator such as a band pass filter. Such a resonator has a component using a distributed constant line or using an inductor together with a capacitor, any of which contains a transmission line. In the resonator, the unloaded Q value is required to be relatively high. Meanwhile, the unloaded Q value can be increased in the resonator by decreasing the loss in the resonator.
The loss in the transmission line includes the dielectric loss, the conductor loss and the radiation loss. The higher the signal frequency is, the more evident the skin effect becomes. Also, the conduct loss will significantly increase. Most of the loss in the resonator derives from the conduct loss. Thus, in order to increase the unloaded Q value in the resonator, it will be effective to decrease the conduct loss. The techniques described in Patent Document 1 and Patent Document 2 are known as the technique for increasing the unloaded Q value in the resonator by decreasing the conductor loss.
A technique has been described in Patent Document 1. In particular, in a resonator with symmetric strip lines, a plurality of strip conductor electrodes are disposed between a pair of ground conductors. In particular, the electrodes are disposed in such a manner that a dielectric is interposed between the plurality of conductors and these electrodes are disposed to be parallel to the ground conductors. Based on this, the conductor loss in the electrodes made of strip conductors is decreased and the unloaded Q value in the resonator is increased.
Patent Document 2 has disclosed a technique. In particular, in a resonator containing strip line electrodes, the strip line electrodes are used as a multilayered electrode containing a multilayered portion and a conductor, wherein the multilayered portion is formed by alternatively stacking a dielectric layer and a conductor layer. In addition, the surface of each layer forming the multilayered portion is disposed to be perpendicular to the surface of a ground conductor. In this way, the conductor loss in the electrodes made of strip lines is decreased and the unloaded Q value of the resonator is increased.
On the other hand, the dielectric line is known as a transmission line for transmitting the electromagnetic waves at a millimetric wave band of about 50 GHz. For example, a transmission line has been disclosed in Patent Document 3 which is configured by disposing a tape with a high dielectric constant between two conductor plates parallel to each other and also disposing a filling dielectric made of a material with a low dielectric constant between these two parallel conductor plates and the tape with a high dielectric constant. As for this transmission line, the electric field of the electromagnetic wave is distributed inside the filling dielectric. It has been described in Patent Document 3 that the actually prepared transmission line has a low dispersing property at the frequency band of 30 GHz to 60 GHz.